You say potato, I say yam

When I spent two months in Nigeria, the term 'yam' was an issue of great contestation between me and my housemate/employer. Ben, always with a huge smirk on his face, insisted that Africa was home to the original yam, and therefore the term yam could only be applied to the white, starchy tuber native to Africa. Those orange things sold as “yams” in the United States were definitely fake yams. 

It was a silly way to poke fun at each other, so neither of us ever really bothered to get to the bottom of the controversy. Besides, Ben knew pretty much everything about everything, so I didn’t question him. And we didn’t have water pressure up to the second floor and our electricity was generator powered, so I didn’t generally spend precious internet time looking up the difference between sweet potatoes and yams.*

But now, with my newfound lack of studenthood, I have lots of disposable internet time to look up questions of such paramount importance. So, let me give it to you straight, straight from the Library of Congress website: Yams sold as such in American supermarkets are not actually yams. They are sweet potatoes. Moreover, according to the U.S. Department of Agriculture, you should KNOW so, because yams are required to be labeled as BOTH sweet potatoes and yams.

How many supermarkets have you been to where this is the case? Either every supermarket I have ever been to is miserably sub par, or there is some lax regulation surrounding the sweet potato/yam conundrum. Election issue, anyone?

Anyway, if you were looking for some actual substance in this post, here it is: while yams and sweet potatoes are both angiosperms, or flowering plants, they are members of different orders and families. Yams are monocots, meaning that they have one embryonic seed leaf, and belong to the family Dioscoreaceae; sweet potatoes are eudicots (having two embryonic seed leaves) and belong to the family Convolvulaceae. Yams are starchier and dryer, with tough skins and usually white interiors (though this varies among the 600 species found in Africa). Sweet potatoes have a variety of skin and flesh tones, and the skin is generally thinner, softer, and edible.

The sweet potatoes Americans have generally come to know as yams are soft sweet potatoes, and were commercially farmed later than their firmer friends. As such, soft sweet potatoes were marketed as yams to differentiate them from their predecessors.

So, why this exegesis on yams vs. sweet potatoes? The recipe I’m about to present you with calls for sweet potatoes, but according to author Anna Thomas, “Yams can be used in place of sweet potatoes if that’s what you have on hand.” Curious cook that I am, I wondered how my soup might have been different had I used sweet potatoes, instead of the yams that were all I could find at my supermarket. Turns out it didn’t make a difference at all, on account of my yams are actually sweet potatoes.

Ok, enough of this nonsense. Here’s the recipe. It’s really lovely, quite light, and makes use of the mix of produce we have available at this time of year; the end of the summer greens, and the beginning of fall and winter’s hard tubers. Of all varieties.

Kale and sweet potato soup with cumin and lemon

Adapted from Anna Thomas’s Love Soup (thanks, Jules!)

2 large leeks, white and light green parts (6 oz.)

1 large yellow onion

2 tbsp olive oil

1 ½ tsp salt (plus more to taste)

12 oz. sweep potatoes

1 small Yukon Gold or white potato

12 oz. Russian kale (I used curly)

4 green onions, sliced

2/3 c. chopped cilantro

freshly ground black pepper

3-4 c. any broth (veggie if you’re trying to keep this vegan, but chicken works fine too)

1 tbsp. cumin seeds

1-2 tbsp. fresh lemon juice

cayenne

Wash and coarsely chop the leeks. A note on leek washing technique; leeks tend to be pretty sandy, so it won’t do to rinse just the outside. The best strategy, I think (thank you Mark Bittman) is to leave both ends of the stalk intact, and cut a long slit through the rest of it the leek; pull apart the two ‘sides’ you have created and run lots of cold water through the layers (see picture). Chop the onion.

Heat the olive oil in a nonstick pan and start sautéing the onion with a sprinkle of salt over medium heat. When the onion is translucent and salt, add the leeks and keep cooking, stirring often, until the vegetables are caramelized and golden, 25-30 minutes.

Meanwhile, peel the sweet potatoes, scrub the non-controversial potato, and cut them all into ½ inch dice. Trim the thick stems from the kale and chop coarsely. Combine potatoes and kale in a soup pot with 5 c. cold water and a teaspoon of salt, bring to a boil, then lower the heat and simmer ~15 minutes.

Add the caramelized onions and leeks to the pot, along with the green onions, cilantro, and a lot of freshly ground black pepper (really! A lot! It’s wonderful!). Add about ~3 c. of broth, or as much as you need to make a soup that pours easily. Simmer gently, covered, for another 10 minutes.

Lightly toast the cumin seeds in a dry pan until they are JUST fragrant (remember , they will keep cooking even when you take them out of the pan) and grind them (with a mortal and pestle if you think it’s quaint and want carpal tunnel…otherwise a spice grinder or cuisinart will do). (Actually toasting and grinding the cumin seeds yourself is worth it for this recipe, as cumin and lemon are the main—and really only—flavor events in this soup. Otherwise it’s quite mild—and you don’t want an insipid soup.)

Stir the cumin and lemon juice into the soup and taste; add more salt, pepper, or lemon juice as needed, and finish with a pinch of cayenne (just a pinch, especially if you’re cooking this ahead of time, as the heat will intensify as the soup sits).

Ladle into bowls and garnish with a swirl of olive oil (I used blood orange olive oil, which was fantastic—but use whatever you have as long as it is high quality! Otherwise, just serve it plain, or with crumbles of feta.).

Serves 6 as a meal

* I did, however, get a look at the NY Times’s “Chocolate Chip Cookies” recipe from the summer of 2008, where they researched everything that is awesome about all chocolate chip cookies baked across NYC and integrated it into a single, singularly awesome chocolate cookie recipe. Priorities are priorities, folks. Sweet potatoes vs. chocolate cookies is no contest.